Method and apparatus for remote optical measurement of the position of a surface

ABSTRACT

Systems and methods for optically measuring a position of a measurement surface relative to a reference position. The system is a wireless network comprising a centrally located data acquisition computer and a multiplicity of remotely located sensor modules mounted at different locations within wireless communication range of a central receiver. Each sensor module is mounted to a clamp that is made specific to a control surface location and embedded with an RFID tag to denote clamp location. The optical components of the sensor modules are selected to enable indication of the linear position of a measurement surface relative to a reference position and then broadcast the measurement results. The broadcast results are received by the central receiver and processed by the data acquisition computer, which hosts human interface software that displays measurement data.

BACKGROUND

The technology disclosed herein relates generally to systems and methodsfor measuring the position of a measurement surface relative to areference position. In particular, the technology disclosed hereinrelates to systems and methods for calibrating steering devices tovehicle operator controls and, more specifically, to rigging aircraftcontrol surfaces to aircraft operator controls.

Fluid dynamics includes the disciplines of aerodynamics andhydrodynamics to optimize fluid flow across control surfaces of avehicle. The control surfaces are precisely moved by the operator duringvehicle movement to create steering forces to direct the vehicle in adesignated path and provide stability during travel. For example, arudder may be adjusted to steer an aircraft or an elevator on ahorizontal stabilizer may be positioned to stabilize lift forces.Complex three-dimensional shapes are often used as control surfaces tooptimize fuel consumption and provide effective operation. These shapesin combination with the other surfaces determine vehicle performancecharacteristics.

Various rigging methods to calibrate control surfaces and relatedsystems are known. A pivotable control surface (e.g., a rudder, anelevator, an aileron or a flaperon) may steer a vehicle (e.g., anaircraft). Deviations of the control surface shape may distort arelationship between the vehicle controls and the control surface.Calibration restores the relationship by establishing an alignmentfeature as part of the control surface which may be aligned to a riggingpoint on the vehicle associated with a known control setting. Ametrology device and/or computer software may be used for calibration.The metrology device may define a positional relationship between areference surface (e.g., an alignment indexing plate comprising aplurality of linear measurement markings) on the vehicle, a rotationalaxis of the control surface, and a target location (e.g., a neutral orzero position) of the alignment feature. By manipulating the controlsurface to a target relationship relative to the reference surface, thelocation of the alignment feature on the control surface may becalibrated relative to the operator controls. In this manner, theoperator controls may be rigged to accurately reflect the true positionof the control surface to improve vehicular performance.

Current tooling for control surface rigging on some aircraft can presentconcerns with respect to ensuring the accuracy of testing and the safetyof aircraft and personnel. There is a need for a system and method thatwould enable a user to measure the positions of various control surfacesfor rigging by non-contact means.

SUMMARY

The subject matter disclosed in detail below is directed to systems andmethods for optically measuring a position of a measurement surfacerelative to a reference position. The system is a wireless networkcomprising a centrally located data acquisition computer and a suite(hereinafter “multiplicity”) of remotely located sensors (hereinafter“sensor modules”) mounted at different locations within wirelesscommunication range of a central receiver. Each sensor module isconfigured to measure a position of a measurement surface relative to areference position and then broadcast the measurement results, whichbroadcast results are received by the central receiver and processed bythe data acquisition computer. The data acquisition computer hosts humaninterface software that displays measurement data.

In accordance with the example embodiments disclosed in some detailbelow, the sensor modules are mounted to an aircraft for use in acontrol surface rigging procedure. A system comprising a multiplicity ofsensor modules mounted to an aircraft and configured to measure aposition of a control surface relative to a reference position and thenbroadcast the measurement results will be referred to hereinafter as a“remote optical control surface indication system”. The remote opticalcontrol surface indication system allows the user to measure thepositions of control surfaces for rigging by non-contact means, thuseliminating the risk of human contact with hazardous aircraft energy.

More specifically, the remote optical control surface indication systemincludes a set of identical sensor modules that are affixed to variousaircraft locations for the purposes of flight controls rigging. Thesensors are equipped with optical components that measure the positionsof flight control surfaces relative to adjacent aircraft geometry.Sensors are indexed to the aircraft by customized clamp assemblies, eachhaving means for identifying the clamp and the sensor attached to theclamp. Measurements are sent wirelessly to a centrally located computerthat hosts a data acquisition (DAQ) software application. The DAQcomputer is capable of sending simple remote commands to the sensormodules. The kit is furnished with sensor zeroing cradle assemblies forsoftware zeroing. When the remote optical control surface indicationsystem is used for the purpose of flight controls rigging, data signalsare generated which indicate when a control surface is at itszero-degree (neutral) position. [As used herein, the terms “zeroposition” and “neutral position” are synonymous.]

In accordance with one proposed implementation, each sensor module ismounted to a clamp that is made specific to a control surface locationand embedded with a radio-frequency identification tag (hereinafter“RFID tag”) to identify the clamp and corresponding location on theaircraft. The clamp indexes the sensor in relation to the controlsurface to be measured. The optical components of the sensor modules areselected to enable indication of the linear position of a flight controlsurface to a specified accuracy. The human interface software displaysmeasurements and/or error states for each specific control surface,allowing the user to make fine adjustments to complete riggingprocedures. However, the system could easily be employed in measuringthings other than aircraft control surfaces, whenever real-timelocation-specific surface height measurements are needed.

The system proposed herein will save time during rigging jobs by notrequiring a human presence at the measurement site. Instead, all sensorswould be set up at once and later used to complete each rigging job inwhichever order the technician desires without needing to communicatewith another technician for manual measurements and without waiting forthat technician to move between measurement locations. Each sensor unitwould be kept in a power save mode (hereinafter “sleep mode”) for longbattery life and “woken up” for each rigging procedure. When eachcontrol surface is within the final rigging tolerance, the user would beable to send the measurement value from the human interface to anaccredited automated test equipment workstation comprising a computerthat is configured to interface with the computers onboard the aircraftand perform an inspection in lieu of a human inspector, saving time inthe process.

Although systems and methods for optically measuring a position of ameasurement surface relative to a reference position will be describedin some detail below, one or more of those proposed implementations maybe characterized by one or more of the following aspects.

One aspect of the subject matter disclosed in detail below is a methodfor optically measuring a position of a measurement surface relative toa reference position, the method comprising: (a) locating a laser deviceso that it has a known location relative to a reference position and isaimed at a measurement surface; (b) projecting a curtain of light in afirst plane from the laser device onto the measurement surface to forman impingement line; (c) detecting an object centroid where lightscattered from the impingement line impinges on a row of photodetectors;and (d) transmitting object centroid data signals that represent ameasured position of the measurement surface relative to the referencesurface. In accordance with some embodiments, step (a) comprisesorienting the sensor module so that the row of photodetectors arealigned in a second plane that is generally perpendicular to the firstplane and intersects the curtain of light.

In accordance with one implementation of the method described in theimmediately preceding paragraph, step (c) comprises: finding anintensity baseline and peak; correcting light intensity for lensvignette artifact; interpolating pixel data for pseudo-sub-pixelresolution; object detection thresholding; and calculating the objectcentroid.

In accordance with some embodiments, the method further comprisesconverting the object centroid data signals to a distance measurementusing stored data representing a table or an equation that correlatespixel values with measured distances in a manner that is characteristicof relative movement of the measurement surface and reference surface.

In accordance with some embodiments, the measurement surface is acontrol surface of an aircraft and the method further comprises:rotating the control surface by discrete degrees of actuation; repeatingsteps (b) and (c) at each discrete degree of actuation until themeasured position of the control surface relative to the referencesurface is a neutral position; and rigging operator controls toaccurately reflect the neutral position of the control surface.

In accordance with other embodiments, the reference surface is a controlsurface of an aircraft and the method further comprises: rotating thecontrol surface by discrete degrees of actuation; repeating steps (c)and (d) at each discrete degree of actuation until the measured positionof the control surface relative to the measurement surface is a neutralposition; and rigging operator controls to accurately reflect theneutral position of the control surface.

Another aspect of the subject matter disclosed in detail below is asensor module comprising: a housing; a laser device mounted inside thehousing and configured to project a curtain of light in a first plane; arow of photodetectors arranged in sequence along a straight line insidethe housing and configured to output respective analog photodetectoroutput signals in response to impingement of light; and a lens mountedinside the housing in front of the row of photodetectors and having afocal axis, wherein a field of view of the lens intersects the curtainof light; and wherein the focal axis of the lens and the straight lineof the row of photodetectors lie in a second plane that is generallyperpendicular to the first plane.

In accordance with some embodiments of the sensor module described inthe immediately preceding paragraph, the sensor module further comprisesa microcontroller that is configured to control operation of the laserdevice and compute a location of an object centroid relative to the rowof photodetectors based on the analog photodetector output signalsoutput by the photodetectors, and a transceiver configured to transmit aradio-frequency signal carrying object centroid data.

A further aspect of the subject matter disclosed in detail below is awireless network comprising: a computer system that hosts dataacquisition software configured to convert object centroid data intodistance measurement data; a central transceiver operatively coupled tothe computer system for receiving a radio-frequency signal carrying theobject centroid data and transmitting the object centroid data to thecomputer system; and a plurality of sensor modules located withincommunication range of the central transceiver, wherein each sensormodule comprises: a housing; a battery; a laser device mounted insidethe housing and configured to project a curtain of light in a firstplane; a row of photodetectors arranged in sequence along a straightline inside the housing and configured to output respective analogphotodetector output signals in response to impingement of light; and alens mounted inside the housing in front of the row of photodetectorsand having a focal axis, wherein a field of view of the lens intersectsthe curtain of light; and wherein the focal axis of the lens and thestraight line of the row of photodetectors lie in a second plane that isperpendicular to the first plane; a microcontroller that is configuredto control operation of the laser device and compute a location of anobject centroid relative to the row of photodetectors based on theanalog photodetector output signals output by the row of photodetectors;and a transceiver configured to transmit a radio-frequency signalcarrying object centroid data representing the location of the objectcentroid computed by the microcontroller, wherein the laser device, themicrocontroller and the transceiver receive electric power from thebattery. In accordance with some embodiments, the plurality of sensormodules are clamped to respective surfaces of an aircraft.

Other aspects of systems and methods for optically measuring a positionof a measurement surface relative to a reference position are disclosedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, functions and advantages discussed in the precedingsection may be achieved independently in various embodiments or may becombined in yet other embodiments. Various embodiments will behereinafter described with reference to drawings for the purpose ofillustrating the above-described and other aspects.

FIG. 1A is a diagram showing: (a) a laser device projecting a lightcurtain in a first plane P1 onto a measurement surface to form animpingement line; (b) a row of photodetectors aligned in a second planeP2 that is generally perpendicular to the first plane P1 and intersectsthe light curtain; and (c) an object centroid D where light scatteredfrom the impingement line impinges on the row of photodetectors.

FIG. 1 is a diagram showing the optical path of the laser light emittedby a sensor module in accordance with one embodiment.

FIG. 2 is a diagram identifying components of a commercially availableoff-the-shelf (COTS) line-emitting laser device that may be part of thesensor module depicted in FIG. 1 in accordance with one proposedimplementation.

FIG. 3 is a graph of pixel data points as a function of measured heightduring movement of a measurement surface in the field of view of thesensor module depicted in FIG. 1.

FIG. 4 is a diagram representing a three-dimensional view of a zeroingjig that can be used to calibrate the sensor module depicted in FIG. 1.

FIG. 5 is a diagram identifying components of the sensor module depictedin FIG. 1 in accordance with one embodiment.

FIG. 6 is a diagram identifying components of the sensor module depictedin FIG. 1 in accordance with one proposed implementation.

FIGS. 7A and 7B are diagrams representing front and rearthree-dimensional views respectively of a sensor module seated in azeroing cradle in accordance with one proposed implementation.

FIG. 8 is a diagram representing a front view of the sensor moduledepicted in FIGS. 7A and 7B with a portion of the housing removed andwithout a zeroing cradle.

FIG. 9 is a diagram representing a partially sectional view of thesensor module depicted in FIGS. 7A and 7B.

FIG. 10 is a diagram depicting physical features on a clamp andmicroswitches incorporated in the bottom of the sensor module fordetecting the physical features on the clamp.

FIG. 11 is a diagram representing an isometric view of an aircrafthaving control surfaces which may be rigged using the apparatusdisclosed herein.

FIG. 12 is a diagram representing a plan view of a wireless network ofsensor modules mounted on an aircraft.

FIG. 13 is a block diagram showing the transmission of data representingmeasured positions of control surfaces from an aircraft to an automatedtest equipment (ATE) station using a wireless network.

FIG. 14 is a flowchart identifying steps of a method for acquiring anddisplaying control surface position measurement data in accordance withone proposed implementation.

FIG. 15 is a diagram showing a graphical user interface being presentedon the display screen of a data acquisition computer in accordance withone embodiment.

FIG. 16 is a diagram representing a side view of an empennage of atypical aircraft.

FIG. 17 is a diagram representing an isometric view of a portion of anempennage having an alignment indexing plate attached to the fuselage.

FIG. 18 is a diagram representing a top view of a rudder having anon-neutral position relative to an alignment indexing plate attached tothe fuselage.

FIG. 19 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a flood mode)and installed for measuring a position of a rudder relative to analignment indexing plate attached to the fuselage in accordance with oneembodiment.

FIG. 20 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a laser mode)and installed for measuring a position of an elevator relative to analignment indexing plate attached to the fuselage in accordance withanother embodiment.

FIG. 21 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a flood mode)and installed for measuring a position of an elevator relative to analignment indexing plate attached to the fuselage in accordance with afurther embodiment.

FIG. 22 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a laser mode)and installed for measuring a position of an aileron relative to a fixedtrailing edge of a wing in accordance with yet another embodiment.

FIGS. 23A and 23B are diagrams representing top and bottomthree-dimensional views respectively of a left-hand (LH) aileron clampin accordance with one proposed implementation.

FIG. 24 is a diagram representing a three-dimensional view of aright-hand (RH) aileron clamp installed (without a sensor module) on afixed trailing edge of a right-hand wing of an aircraft.

FIG. 25 is a diagram representing a three-dimensional view of somecomponents of an aileron clamp assembly for installation in theembodiment depicted in FIG. 22.

FIG. 26 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a laser mode)and installed for measuring a position of a flaperon relative to a flapin accordance with a further embodiment.

FIGS. 27A and 27B are diagrams representing top and bottomthree-dimensional views respectively of a right-hand (RH) flaperon clampin accordance with one proposed implementation.

FIG. 28 is a diagram representing a three-dimensional view of somecomponents of a flaperon clamp assembly for installation in theembodiment depicted in FIG. 23.

FIG. 29 is a diagram representing a bottom view of the indexing of an RHflaperon clamp (with a sensor module) clamped to the outboard edge of aninboard flap in accordance with another proposed implementation.

FIG. 30 is a diagram representing an end view of an elevator clampinstalled (without a sensor module) on a trailing edge of an elevator.The elevator clamp features an indicator flag to ensure the clamp hasnot been moved subsequent to installation.

Reference will hereinafter be made to the drawings in which similarelements in different drawings bear the same reference numerals.

DETAILED DESCRIPTION

Illustrative embodiments of systems and methods for optically measuringa position of a measurement surface relative to a reference position aredescribed in some detail below. However, not all features of an actualimplementation are described in this specification. A person skilled inthe art will appreciate that in the development of any such actualembodiment, numerous implementation-specific decisions must be made toachieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

The system is a wireless network comprising a centrally located dataacquisition computer and a multiplicity of remotely located sensormodules mounted at different locations within wireless communicationrange of a central receiver (e.g., a USB dongle plugged into a USB portof the data acquisition computer). Each sensor module is configured tomeasure a position of a measurement surface relative to a referenceposition and then broadcast the measurement results, which broadcastresults are received by the central receiver and processed by the dataacquisition computer. Before specific implementations of such a wirelessnetwork are described, the basic principle underlying the opticalmeasurement technique employed by the sensor modules will be describedin some detail.

FIG. 1 is a diagram showing the optical path of the laser light emittedby a sensor module 2 that is attached to a clamp 4 in accordance withone embodiment. In this example, the clamp 4 is coupled to a referencesurface 6, which reference surface 6 is disposed adjacent to ameasurement surface 8 (such as a pivoting control surface on anaircraft). The sensor module 2 is configured to measure the position(e.g., the height h) of the measurement surface 8 relative to a zero(reference) position indicated by the solid line at h=0 in FIG. 1between two dashed lines. The upper dashed line represents an instancein which the measurement surface 8 is at a height h above the referenceposition (h=0); the lower dashed line represents an instance in whichthe measurement surface 8 is at a height −h below the reference position(h=0).

The sensor module 2 includes a housing 42 and a battery (not shown, butsee battery 30 in FIG. 4) contained within the housing 42. The sensormodule 2 further includes a line-emitting laser device 36 (hereinafter“laser device 36”). The laser device 36 is mounted inside the housing 42and is configured to project a curtain of light (hereinafter “lightcurtain A”) in a first plane that is oriented perpendicular to the pagein FIG. 1. When the light curtain A impinges on the measurement surface8, a laser line C (again extending perpendicular to the page in FIG. 1)is formed.

In one implementation, the laser device 36 is a VLM-635-27-LPA laserdiode manufactured by Quarton, Inc., Taipei City, Taiwan. TheVLM-635-27-LPA laser diode uses a simple cylindrical lens made of quartzand transmits light having a center wavelength of 635 nm. Thecylindrical lens converts the laser beam into a curtain of light in aplane. The curtain of light is directed onto the measurement surface.

In an alternative implementation, a laser device having a rotatingpolygonal mirror may be used to produce the laser line C. FIG. 2 is adiagram identifying components of a line-emitting laser device 36 thatis suitable for use in the position measurement system proposed herein.The laser device 36 depicted in FIG. 2 includes a polygonal mirror 188mounted on the output shaft of a motor 190. Rotation of the polygonalmirror 188 is controlled by a motor controller 186 which receives clockpulses from a clock (not shown) and converts those clock pulses intomotor drive pulses. The laser device 36 depicted in FIG. 2 furtherincludes a laser driver 181 that drives a laser 182 to generate acontinuous-wave or pulsed laser beam that is directed at a mirror 184(or other reflective surface). The mirror 184 is oriented such that theprojected laser beam is reflected onto the polygonal mirror 188 rotatingat high speed in exact synchronism with the clock pulses from the clock.As the angle of each reflective facet of the polygonal mirror 188changes during rotation, a line-emitting laser beam A is reflected byeach facet onto a collimating lens 192. The reflected beam sweeps acrossthe input surface of the collimating lens 192, but the photons changedirection as they propagate through the collimating lens 192, exitingthe collimating lens 192 in parallel.

Referring again to FIG. 1, the sensor module 2 further includes acompound lens 16 (hereinafter “lens 16”) and a linear array ofphotodetectors 18 arranged in sequence to form a row along a straightline inside the housing 42. The lens 16 is mounted inside the housing 42in front of the row of photodetectors 18. The photodetectors 18 areconfigured to output respective analog photodetector output signals inresponse to impinging light.

In the instance wherein the measurement surface 8 is at the zeroposition (indicated by the solid horizontal straight line labeled “8” inFIG. 1), the impingement of the light curtain A on the measurementsurface 8 produces the laser line C. The measurement surface 8 in turnscatters that impinging light of laser line C. Some of the scatteredlaser light enters the lens 16 and is detected by the row ofphotodetectors 18. In the scenario depicted in FIG. 1, the lightimpinging on the row of photodetectors 18 includes scattered light fromlaser line C.

FIG. 1A is a diagram showing the laser device 36 projecting a lightcurtain A in a first plane P1 onto a measurement surface 8 to form animpingement line C and a row of photodetectors 18 aligned in a secondplane P2 that is generally perpendicular to the first plane P1 andintersects the light curtain A. FIG. 1A also indicates an objectcentroid D where light scattered from the impingement line C impinges onthe row of photodetectors 18.

To better explain the optical measurement technique used by the sensormodule 2, the following discussion assumes that the reference surface 6and measurement surface 8 depicted in FIG. 1 are planar and thatmeasurement surface 8 is part of a component that is pivotable about anaxis that is parallel to the plane of the measurement surface 8. As thecomponent pivots, the measurement surface 8 moves up or down (asdepicted by arrows in FIG. 1) in dependence upon the direction ofcomponent rotation. Rotational motion is approximated as linear (up anddown) motion at the measurement area. This is a reasonable approximationbased on the small-angle formula.

Preferably the sensor module 2 is situated so that the laser device 36transmits the light curtain A downward at an angle φ (measured relativeto a reference plane of the sensor module 2) onto the measurementsurface 8, thereby projecting a generally horizontally oriented laserline C onto the measurement surface 8. In contrast, the lens 16 isarranged so that the focal axis B of lens 16 is directed downward at anacute angle θ relative to the light curtain A. In addition, the focalaxis B of lens 16 and the straight line of the row of photodetectors 18lie in a second plane (disposed in the plane of the page in FIG. 1) thatintersects the first plane (disposed perpendicular to the plane of thepage in FIG. 1) in which the light curtain A lies.

The impinging light from laser line C is scattered in all directions bythe measurement surface 8, including toward the lens 16. However, thevertically oriented linear array of photodetectors 18 only sees a thincross section of the laser line C (analogous to a horizon line beingviewed through a tall narrow window). In the parlance of computer visionobject tracking, the “object” is the real-world target. In this case,the object is the laser line C, and the centroid of the object is thepoint at the center of the thin cross section of the laser line whichimpinges on the linear array of photodetectors 18. (The thin slice, or“cross section” of the laser line rises and falls in intensity from topto bottom (or vice versa); the intensity of the cross section peaks inthe center, with the falloff following the Gaussian distribution.)

The position of the impingement of the laser light onto thephotodetector (or photodetectors) is a function of the apparent height d(see FIG. 1) of the measurement surface 8. The apparent height d is afunction of the actual height h. Thus the row of photodetectors 18 maybe used to measure the height h of the measurement surface 8 thatscattered the laser line toward the photodetector array.

More specifically, the theoretical relationship between actual height hand apparent height d is d=(h/cos(φ))sin(θ). The actual mathematicalrelationship is dependent on the geometry of the compound lens 16 andmanufacturing variables. An example empirical equation relating beamposition x in pixels to actual height h is:

$x = {{2\sqrt{\frac{5}{286511}}\sqrt{{250h} - {9141}}} - \frac{3934}{3125}}$

For the sake of illustration, assume that the focal axis B of lens 16intersects the laser line C when the measurement surface 8 is in themiddle position indicated in FIG. 1 by the horizontal solid straightline labeled h=0 (which condition is unnecessary to practice of themethod of measurement disclosed herein). In that scenario, theparticular photo-detectors that detect a centroid of the scattered lightfrom laser line C will vary in position as the measurement surface 8moves up to the upper position indicated in FIG. 1 by the horizontaldashed straight line labeled +h. Similarly, the particularphotodetectors that detect a centroid of the scattered light from laserline C will vary in position as the measurement surface 8 moves down tothe lower position indicated in FIG. 1 by the horizontal dashed straightline labeled −h. In other words, the position of the centroid-detectingphotodetector (or pair of centroid-detecting photo-detectors) varies asthe position of the measurement surface varies.

FIG. 3 is one example of a graph of pixel data points as a function ofmeasured height. The pixel data points (which form a sensor responsecurve) were generated after an interpolation process (executed by amicrocontroller, described in some detail below) that doubles the numberof data points by injecting a new data point between each existing oneon the linear array of photodetectors 18. The pixel data points are thenprocessed to derive an object centroid calculated in units of pixels.

The object centroids are plotted in FIG. 3, and those outputs are usedto generate the overall sensor response curve, which is an account ofthe output centroids in units of pixels versus the actual heightposition of the measurement surface. The centroid calculation uses pixelintensity thresholding (as described below with reference to FIG. 14).All of the pixel calculations use only the data gathered by the pixelphotodetectors.

Before the sensor module 2 is ready for use in a rigging operation, thesensor module 2 should be calibrated. FIG. 4 is a diagram representing athree-dimensional view of a zeroing jig 194 that can be used tocalibrate the sensor module 2. The zeroing jig 194 has a sensor modulesupport surface 195, a laser zeroing surface 196 and a flood zeroingline 198. While operating in the laser mode, the sensor module 2 iscalibrated by determining which photodetector detects the objectcentroid when the sensor module 2 emits a light curtain A that impingeson the laser zeroing surface 196. The position of the laser zeroingsurface 196 relative to the sensor module frame of reference is selectedto match the neutral position of the control surface when the sensormodule 2 is installed. In one implementation, the standard height of thesensor assembly from the neutral plane is ½ inch.

The zeroing function is started by either booting the sensor module 2 onthe zeroing jig 194 or placing the sensor module 2 onto the zeroing jig194 after the sensor module 2 has been turned on but prior to placingthe sensor module 2 on any clamp. The zeroing jig 194 has an RFID taglike the clamps do, so that the sensor module 2 device knows when it ison the zeroing jig 194. The zeroing process starts automatically whenthe zeroing jig 194 is detected.

The sensor module 2 is also operable in a flood mode. In the flood mode,an array of light-emitting diodes (LEDs) (not shown in FIG. 1, but seeLED array 34 in FIGS. 5 and 25) are activated to project light thatilluminates the flood zeroing line 198. While operating in the floodmode, the sensor module 2 is calibrated by determining whichphotodetector detects the object centroid when the sensor module 2 emitsa flood of light that impinges on the flood zeroing line 198 and areasadjacent thereto. In this case, the object centroid is due to light notscattered toward the photodetectors by the flood zeroing line 198.

FIG. 5 is a diagram identifying components of the sensor module 2depicted in FIG. 1 and a component (RFID tag 26) that is part of theclamp in accordance with one embodiment. The sensor module 2 includes abattery pack 30 that provides power to all of the electrical-powereddevices onboard the sensor module 2. In one proposed implementation, thebattery pack 30 includes six AA batteries. In one proposedimplementation, the battery pack 30 includes rechargeable lithium-ionbatteries.

The electrical-powered devices contained within housing 42 of the sensormodule 2 include a microcontroller 20, a transceiver 24, an RFID module28, an LED array 34, a line-emitting laser device 36, and a linearcharge-coupled device array 46 (hereinafter “linear CCD array 46”). Thelinear CCD array 46 includes the aforementioned linear array ofphotodetectors 18. More specifically, pixels are represented by p-dopedmetal-oxide-semiconductor (MOS) capacitors. These capacitors are biasedabove the threshold for inversion when image acquisition begins,allowing the conversion of incoming photons into electron charges at thesemiconductor-oxide interface. The CCD array 46 then reads out thesecharges to the microcontroller 20.

The sensor module 2 further includes optical components arranged in thefollowing sequence within housing 42: a polarization filter 12, abandpass filter 14. a compound lens 16 and a row of photodetectors 18.The scattered light from the laser line C passes through thepolarization filter 12, which attenuates light that is not oriented inthe direction parallel to the surface to aid in isolation of reflectedlaser light. The polarization filter 12 reduces glare and outside lightinterference. In one implementation, the bandpass filter 14 is a pieceof red coated glass that has a transmission curve with a sharp peak atthe same wavelength as the laser light (e.g., 635 nm) and a highextinction coefficient at other wavelengths. This filters out themajority of outside interference light, thereby isolating the laserlight from ambient light. The filtered light then impinges on thecompound lens 16. The single row of photodetectors (pixels) are orientedvertically and aimed downward toward the measurement surface 8 at apreset angle. The photodetectors 18 capture laser light scattered fromthe measurement surface 8. In one implementation, the linear arrayincludes 128 photodetectors (pixels).

Still referring to FIG. 5, the photodetectors 18 output analogphotodetector output signals (hereinafter “pixel data”) to amicrocontroller 20. The microcontroller 20 connects to all peripheralsand handles logic input/output, serial communication, sensor inputs andpower distribution. The microcontroller 20 is configured to execute alaser line tracking algorithm that includes the following operations:finding an intensity baseline and peak, correcting light intensity forlens vignette artifact, interpolating the pixel data forpseudo-sub-pixel resolution, object detection thresholding andcalculation of the object centroid. The microcontroller 20 is alsoconfigured to output serial payload containing object centroid data interms of pixel numbers indicating which photodetectors detected theobject centroid. In accordance with one implementation, the serial datais output at a rate of about 20 Hz. The microcontroller 20 receiveselectric power from the battery pack 30 via a voltage divider 32. Thevoltage divider 32 scales battery voltage down for analog voltagereading.

The microcontroller 20 outputs the serial data to a transceiver 24 via atransceiver interface 22. The transceiver 24 handles the networkcommunication protocol. In one implementation (described in more detailbelow with reference to FIGS. 9 and 10), the network is a Zigbee network60. Zigbee is an IEEE 802.15.4-based specification for a suite ofhigh-level communication protocols used to create close-proximity areanetworks with small, low-power digital radios.

The microcontroller 20 also controls the operation of the laser device36 and the LED array 34. As previously described with reference to FIG.1, the laser device 36 emits a light curtain A that is aimed downwardtoward the measurement surface 8 at a preset angle, forming ahorizontally oriented laser line C when the light curtain A impinges onthe measurement surface 8. In one implementation, the emitted laserlight has a wavelength range that is centered at 635 nm (red). The LEDarray 34 illuminates the measurement surface 8 (or optical target) inlieu of laser light in some applications (described in more detailbelow).

In accordance with one embodiment, the sensor module 2 further includesan RFID module 28 that is configured to read an RFID tag 26 which isembedded in the clamp assembly to which the sensor module 2 is mounted.The RFID tag identifies which clamp assembly that sensor module 2 ismounted to. Since the identity and location on the aircraft of eachclamp assembly are known, the identification of the clamp assemblyenables a centrally located computer to determine which control surfaceis being measured remotely.

FIG. 6 is a diagram identifying components of the sensor module 2depicted in FIG. 1 in accordance with one proposed implementation. Inthis implementation, the photodetectors 18 are incorporated in a linearCCD array 46 that is mounted to a sensor board. The compound lens 16 isa 12-mm lens mounted to the same sensor board. The linear CCD array 46has a single row of photodetectors (pixels) oriented vertically andaimed downward toward the measurement surface 8 at a preset angle. Thelinear CCD array 46 captures laser light scattered from the measurementsurface 8.

In one implementation, the linear CCD array 46 is a TAOSTSL1401R128-pixel linear array sensor (commercially available from TexasAdvanced Optoelectronic Solutions, Plano, Tex.). The TSL1401R chipconsists of a single row of 128 photodetectors. The lens 16 forms imageson the sensor array. The camera processor 48 starts and stops exposures,and then responds to clocking pulses with the voltage levels of eachincrementing pixel. The microcontroller 20 reads off the pixel values.The camera module 40 allows a host system to “see” in one dimension.

The microcontroller 20 handles all analog and digital inputs andoutputs, runs the sensor module programming, and stores the zeroposition to EEPROM memory. In one implementation, the mainmicrocontroller board is an Arduino Mega 2560 microcontroller board,which has 54 digital input/output pins (of which 15 can be used as PWMoutputs to the LED array 34), 16 analog inputs, four UARTs (hardwareserial ports) (one of which is used to connect the camera board to themain microcontroller board), a 16-MHz crystal oscillator, a USBconnection, and a power jack.

The microcontroller 20 also controls the on/off state of the LED array34, but it does so via switches 25. In one implementation, the switches25 include two reverse-biased MOSFET transistors: one for the flood LEDarray 34 and one for the laser device 36. The camera module 40 ispowered while the sensor module is in the sleep mode. The LED array 34includes three individual LEDs powered by DC current. In oneimplementation, the three LEDs are powered by three 2-V linear voltageregulators, which are in turn all powered by the one MOSFET designatedfor switching LED power. All three voltage regulators and the twoMOSFETs are found on a “jumper board” (not shown in the drawings), whichalso holds three resistors for an RGB indicator LED 132, two pull-downresistors for biasing the MOSFETs, a USB port wired in parallel with theArduino's native USB port, and screw terminals for all of theperipherals and power connections. The jumper board sits on top of thetransceiver interface board and has through pins for access to all ofthe Arduino pins. The main purpose of the jumper board is to ease finalassembly by providing strong terminal connections and to hold thoseother components. In the implementation partly depicted in FIG. 6, thetransceiver 24 is an Xbee radio module operating at 2.4 GHz, and thetransceiver interface 22 is an Xbee shield that interfaces with theArduino microcontroller and provides power to the Xbee radio. Themicrocontroller 20 communicates with the transceiver 24 via thetransceiver interface 22. The transceiver 24 is capable of wirelesslyrelaying measurements and commands between the microcontroller 20 and acentrally located data acquisition computer (hereinafter “DAQcomputer”).

In one implementation, the transceiver 24 is an Xbee Pro S1 802.15.4module, while the transceiver interface 22 is a Seeedstudio Xbee shieldwith a serial peripheral interface (SPI) pass-through suitable forrouting signals between Xbee radios and Arduino microcontroller boards.(A “shield” is any board that is made to fit the layout and plug rightinto an Arduino microcontroller board.) The Xbee Pro S1 802.15.4 moduleis mounted on the Seeedstudio Xbee shield. The latter provides power tothe former, contains circuitry for logic input/output, and allows theuser to select serial pins with jumpers. The Xbee Pro S1 802.15.4 modulehas its own processor built in. The Xbee is pre-programmed prior toinstallation and then sends and receives data to and from the Arduinomicrocontroller board. Once the Xbee is programmed and installed, itoperates autonomously.

The battery pack 30 supplies constant-voltage power. Battery power goesstraight from the on/off switch to the microcontroller 20 and thevoltage divider 32, which are wired in parallel. The microcontroller 20in turn supplies appropriate voltages to the display screen 44, thetransceiver interface 22, and the RGB indicator LED 132. The RGBindicator LED 132 is mounted on the housing 42 of the sensor module 2and serves to indicate when the device is turned on, when a valid targethas been detected, and when an error state is indicated. In particular,the RGB indicator LED 132 illuminates in different colors to conveystatus information at a distance.

The microcontroller 20 also controls the display screen 44. In oneimplementation, the display screen 44 is a liquid crystal display (LCD)screen that displays sensor status information useful for workflow andtroubleshooting.

FIGS. 7A and 7B are diagrams representing front and rearthree-dimensional views respectively of a sensor module 2 in accordancewith one proposed implementation. The housing 42 of the sensor module 2has a flat base 76 that is designed to sit flush on a clamp. A pair ofcatches 33 a and 33 b (only one of which is visible in FIGS. 7A and 7B,but see FIG. 8) are fastened to opposing end walls 78 a and 78 b of thehousing 42. As will be described in some detail below with reference toFIGS. 26a and 28A, respective latches are latched onto the catches 33 aand 33 b to hold the sensor module 2 onto the clamp. The housing 42 hasan opening (not visible in FIGS. 7A and 7B) in a top wall that is closedby a battery cap 47. The battery cap 47 is removed before inserting orremoving batteries.

After the sensor module 2 has been mounted to a clamp, which clamp hasin turn been attached to a reference surface, the sensor module isturned on manually by pressing the main power button 45 situated on topof the housing 42. The microcontroller 20 is configured to default tothe sleep mode in response to activation of the module. In response toreceipt of a “wake” command from a central station, the remotely locatedsensor module 2 changes to the laser mode. In response to detection of aflood command encoded in the RFID tag 26, the sensor module 2 changes tothe flood mode.

As shown in FIG. 7A, the housing 42 includes an optical scaffold 136that holds the camera board assembly, the laser device 36, the LED array34, two light filters, and a polycarbonate laser aperture pane. Theoptical scaffold 136 is permanently bonded to the rest of the housing42. The optical scaffold 136 has a surface configuration designed to notblock light transmitted from or backscattered to the optical componentsinside the housing 42. In the implementation depicted in FIG. 7A, thesurface configuration of the optical scaffold 136 includes a concavity136 a having a planar surface that is generally parallel to the plane inwhich the light curtain A propagates. The concavity 136 a has anaperture 43 that is aligned with the laser device 36. The surfaceconfiguration of the optical scaffold 136 further includes a concavity136 b having a planar surface that is generally parallel to an axis ofthe LED array 34. The concavity 136 b has an aperture that is alignedwith the LED array 34. The surface configuration of the optical scaffold136 further includes a concavity 136 c having an aperture that isaligned with the lens 16.

As shown in FIG. 7B, the housing 42 also includes a removable rearaccess panel 134 that allows access to the interior of the housing 42when removed. The rear access panel 134 has one opening for a displayscreen 44 and another opening for an optically transparent hemisphericalLED bubble 130. The RGB indicator LED 132 protrudes through the rearaccess panel 134 and into an alcove within the LED bubble 130.

FIG. 8 is a diagram representing a front view of the sensor moduledepicted in FIGS. 7A and 7B with the optical scaffold 136 and othercomponents removed. The axis of the laser device 36 is disposed at apreset angle φ (see FIG. 1) relative to a vertical mid-plane of thehousing 42. Likewise the focal axis of the lens 16 is disposed at apreset angle (φ+θ) relative to the vertical mid-plane of the housing 42.

FIG. 9 is a diagram representing a partially sectional view of thesensor module depicted in FIGS. 7A, 7B and 8. As seen in FIG. 9, thecamera module 40 includes linear CCD array 46 and lens 16. The laserdevice 36 and camera module 40 are oriented at the respective presetangles described in the preceding paragraph and shown in FIG. 1. The LEDarray 4 is installed between the laser device 36 (situated above) andthe camera module 40 (situated below). The laser device 36 is capable ofemitting a laser line on an area of a measurement surface 8 within thefield of view of the camera module 40 in a laser mode. The LED array 34is capable of illuminating the same area of the measurement surface 8 ina flood mode.

In accordance with an alternative embodiment of the sensor module 2, theRFID reader may be replaced by a microswitch array. FIG. 10 is a diagramdepicting physical features 5 a and 5 b on a clamp 4 and microswitchesSW1, SW2 and SW3 of a microswitch array 19 incorporated in the bottom ofthe sensor module 2. FIG. 10 depicts an instant in time when the sensormodule 2 is not yet in contact with the clamp 4. When the sensor module2 is placed flush on the clamp 4, the microswitch array 19 detects thephysical features 5 a and 5 b on the clamp 4. That information will beused to identify the clamp 4. FIG. 10 presents a simple example encodingscheme in which the three microswitches SW1, SW2 and SW3 overlierespective encoding areas on the clamp when the sensor module 2 andclamp 4 are properly aligned. The encoding scheme is realized by formingor not forming physical features in the respective encoding areasdepending on the identification code of the particular type of clampbeing used and then using the microswitch array 19 to detect thepresence of the physical features representing that identification code.In the example depicted in FIG. 10, physical feature 5 a has been builton a first encoding area, physical feature 5 b has been built on a thirdencoding area, and no physical feature has been built on a secondencoding area disposed between the first and third encoding areas. Thestate of the outputs of the microswitches SW1, SW2 and SW3 represents aswitch combination that is sent to the microcontroller 20 by way of amultiplexer 21.

In accordance with the example embodiments disclosed in some detailbelow, the sensor modules 2 are mounted to an aircraft 100 (e.g., seeFIG. 12) for use in a control surface rigging procedure. A systemcomprising sensor modules and clamping assemblies mounted to an aircraftand configured to measure a position of a control surface relative to areference position and then broadcast the measurement results will bereferred to hereinafter as a “remote optical control surface indicationsystem”. The remote optical control surface indication system disclosedherein allows the user to measure the positions of control surfaces forrigging by non-contact means, thus eliminating the risk of human contactwith hazardous aircraft energy.

FIG. 11 is a diagram representing an isometric view of an aircraft 100having control surfaces which may be rigged using the remote opticalcontrol surface indication system disclosed herein. The aircraft 100includes a fuselage 104, a pair of wings 101 a and 101 b, and anempennage 102. The aircraft 100 further includes two propulsion units108 a and 108 b respectively mounted to the wings 101 a and 101 b.

Still referring to FIG. 11, the empennage 102 includes a verticalstabilizer 106, used to restrict side-to-side motion of the aircraft(yawing), and a rudder 54 pivotably coupled to the vertical stabilizer106 by hinges. The rudder 54 is rotatable to provide the appropriateyawing force according to a corresponding deflection angle. Theempennage 102 further includes a horizontal stabilizer 110, which isused to provide pitch stability. The rear section of the horizontalstabilizer has left-hand and right-hand elevators 58 a and 58 bpivotably coupled thereto by hinges. An elevator is a movableairfoil-shaped body that controls changes in pitch, i.e., theup-and-down motion of the aircraft's nose. The aircraft 100 depicted inFIG. 11 also includes one or more leading edge devices (not described indetail herein) and one or more trailing edge devices (some of which aredescribed in some detail below) which may be extended and/or retractedto alter the lift characteristics of the wings 101 a and 101 b. As seenin FIG. 11, the wings 101 a and 101 b also include trailing edge deviceslocated at the trailing edges of the wings. In the example depicted inFIG. 11, the trailing edge devices include left-hand and right-handinboard flaps 55 c and 55 d and left-hand and right-hand outboard flaps55 a and 55 b. In addition, the trailing edge devices include aleft-hand flaperon 56 a and a left-hand aileron 52 a on the left wing101 a as well as a right-hand flaperon 56 b and a right-hand aileron 52b on the right wing 101 b. A flaperon is a type of control surface thatcombines the functions of both flaps and ailerons.

The apparatus disclosed herein, including clamping assemblies and sensormodules, may be mounted to the aircraft 100 and utilized to rig theleft-hand aileron 52 a, the right-hand aileron 52 b, the rudder 54, theleft-hand flaperon 56 a, the right-hand flaperon 56 b, the left-handelevator 58 a and the right-hand elevator 58 b. In accordance with oneproposed implementation, each sensor module 2 is mounted to a clamp thatis made specific to a respective control surface location on anaircraft.

FIG. 12 is a diagram representing a plan view of a wireless network ofsensor modules 2 mounted on an aircraft 100. The sensor modules 2 aremounted to the aircraft 100 at locations where the zero positions ofvarious control surfaces are measured during a rigging procedure. Thecontrol surface position data acquired by the sensor modules 2 iswirelessly transmitted to a data acquisition computer 62 (see FIG. 13).That information is ultimately received by automated test equipment 64(hereinafter “ATE 64”) for use in a control surface rigging procedure.

The ATE 64 includes a system controller that has a memory for storingprogrammed instructions that control operation of the test apparatus toautomatically test the flight controls system of the aircraft 100, andfor storing the resulting flight controls system test data. In addition,the apparatus includes components enabling an operator to enterinformation into, and output test data from, the system controller. Aninterface comprising the automated test apparatus connects the systemcontroller to the aircraft flight controls system, enabling the systemcontroller to automatically control the flight controls system inaccordance with the programmed instructions, to effect the variousfunctions of the flight controls system in order to test the flightcontrols system operation on the ground. In one embodiment, the ATE 64is connected by the interface to an onboard central maintenance computerwithin the aircraft's flight equipment. The central maintenance computeris connected to the flight controls system of the aircraft, including aplurality of LRUs and control surface transducers. The centralmaintenance computer includes a non-volatile memory and is programmed torun onboard tests of the flight controls system. When connected, thesystem controller controls the central maintenance computer inaccordance with the programmed instructions to run the onboard tests ofthe flight controls system, with results of the onboard tests beingconveyed through the interface for storage by the system controller.

FIG. 13 depicts the transmission of data representing measured positionsof control surfaces from an aircraft to an automated test equipment(ATE) station using a wireless network. More specifically, sensormodules measure the positions of ailerons 52, rudder 54, flaperons 56and elevators 58 and then transmit the acquired data (e.g., the objectcentroid data signals) to a data acquisition computer 62 via a Zigbeenetwork 60. Zigbee is an IEEE 802.15.4-based specification for a suiteof high-level communication protocols used to create close-proximityarea networks with small, low-power digital radios. The object centroiddata signals are received by a USB dongle which is plugged into a USBport of the data acquisition computer 62.

The data acquisition computer 62 hosts a data acquisition softwareapplication that processes the object centroid data signals receivedfrom the sensor modules 2. The raw data and processed data are stored ina data repository 72, which is a non-transitory tangiblecomputer-readable storage medium.

The system controller of the ATE 64 is a computer configured to poll thedata acquisition software application for measurements to perform apass/fail test 70. Digital test results are stored by the systemcontroller and may be relayed for storage in a build verificationdatabase 74 that coordinates integrated aircraft systems testing. Thebuild verification database 74 is stored in non-transitory tangiblecomputer-readable storage medium (e.g., a server).

Still referring to FIG. 13, the control surface rigging process isperformed by a user 66 via a ground test 68, which is a computer programthat is run either on the aircraft's computers or on a laptop with aconnection to the aircraft. The ground test program is part of theaircraft design, and is tied into various aircraft systems. Ground testsmay be run from the flight deck or from the ATE system controller.Readouts are used to adjust hydraulics during the ground test. Theground test program executes a sequence of hardware and softwareoperations to fill and bleed the hydraulic systems, and at certainpoints asks the user 66 to physically zero out the position of eachcontrol surface. This is achieved through “bumps” of hydraulic actuationinitiated by the user 66 from in the ground test 68. The user clicks theup and down buttons to move each control surface by small, discretedegrees of actuation until the measurement surface is as close aspossible to flush (zero) with the adjacent wing surface. When this hasbeen physically verified, the user 66 clicks another button within theground test 68 to accept the current position as the new zero. Thispoint is stored in the aircraft's memory, and the ground test 68 thenenters into a sequence of hydraulic maneuvers that zero the controlsurface's other actuation devices to the new zero position. When this iscompleted, the ground test 68 prompts the user 66 to move on and do thesame thing to the next control surface.

FIG. 14 is a flowchart identifying steps of a method 200 for acquiringand displaying control surface position measurement data in accordancewith one proposed implementation. The linear CCD array 46 detects laserlight scattered from the measurement surface and outputs an array ofpixels (step 202). The microcontroller 20 acquires the pixel array,converting analog voltages to digital voltages (step 204). Then themicrocontroller 20 calculates an intensity baseline (step 206), executesa lens cosine error correction algorithm (step 208), iterates theintensity baseline calculation (step 210), interpolates the pixel arrayvalues (step 212), applies detection thresholding criteria (step 214),calculates the object centroid in units of pixels (step 216), and thentransmits a sensor payload that includes the object centroid data (step218). The sensor payload is received by the data acquisition computer 62via radio receiver (step 220). The data acquisition computer 62 parsespixel value, sensor identity, serial number, etc. (step 222). The serialnumber is used to retrieve the appropriate sensor response curveequation for the identified control surface (step 224). Then the dataacquisition computer 62 converts the pixel output value to an inchmeasurement (step 226), converts the inch measurement to hashmarks asneeded (step 228), and displays the measurement output in a graphicaluser interface (step 230).

Interpolation artificially increases the measurement resolution into thesub-pixel regime. This is done under the assumption that the measurementsurface is smooth and flat enough at small scales so that one can safelymake up pixel intensity values and insert them between the existingones. This is done by simple averaging between nearest neighboring pixelintensity values.

As used herein, a hashmark refers to a particular degree of flightcontrol surface movement at the hydraulic actuator. Specifically, ahashmark is a linear measurement at the trailing edge of the controlsurface corresponding to 0.05 degree of rotational movement at theactuator. This definition is tied to the aerodynamic requirements of theaircraft, and hashmarks form the basis for rigging requirements. Not allrigging requirements are explicitly written on the basis of hashmarks,but in cases where hashmarks are used, the units of control surfacemovement are converted from inch measurements to hashmarks. The DAQcomputer 62 first calculates the measurement in terms of inches and thentranslates the output into hashmarks.

FIG. 15 is a diagram showing a graphical user interface 80 beingpresented on the display screen 96 of the data acquisition computer 62.The graphical user interface 80 includes a menu 82 having a number ofcolumns. The CONTROL SURFACE column lists the names of the controlsurfaces involved in the rigging procedure. The system operator mayselect any one of the control surfaces for rigging by clicking on theassociated field in the row that names the control surface to beselected. The CLAMP ID column lists the respective ID code for each ofthe listed control surfaces. The instructions for initiating a dataacquisition for a selected control surface are visible in a window 92.The system operator may scroll down to see additional information inwindow 92.

The process for initiating a data acquisition includes selecting acontrol surface to be rigged by clicking on a field in the SELECT columnof menu 82 and then turning on the sensor module associated with theselected control surface by touching a SCAN virtual button 84. Theselected sensor module is then awakened by touching a WAKE virtualbutton 86. The same sensor module may be switched to the sleep mode bytouching a SLEEP virtual button 88. The rigging procedure may beterminated by touching a STOP virtual button 90.

The rigging methods disclosed in detail herein may be used to calibrateailerons, flaperons, elevators, rudders and other types of controlsurfaces by optically detecting the position of a measurement surfacerelative to a reference position. In some cases, the measurement surfaceis movable and the reference surface (to which the sensor module isclamped) is fixed; in other cases, the measurement surface is fixed andthe reference surface is movable.

For the sake of illustration, a process for rigging a rudder will bedescribed in some detail. FIG. 16 shows the structure of a typicalempennage 102 of an aircraft. The vertical tailfin of the typicalempennage 102 includes fixed front section called the verticalstabilizer 106, used to restrict side-to-side motion of the aircraft(yawing). The vertical stabilizer 106 is attached to the top of a rearportion of the fuselage 104. The rear section of the vertical tailfintypically has a rudder 54 pivotably coupled to vertical stabilizer 106by hinges. The rudder 54 is rotatable to provide the appropriate yawingforce according to a corresponding deflection angle. The typicalempennage 102 depicted in FIG. 13 further comprises a horizontalstabilizer 110, which is used to provide pitch stability. The rearsection of the horizontal stabilizer 110 typically has elevators 58 aand 58 b pivotably coupled to the horizontal stabilizer 110 by hinges(only elevator 58 a is visible in FIG. 16). An elevator is a movableairfoil-shaped body that controls changes in pitch, i.e., theup-and-down motion of the aircraft's nose.

Various rigging methods may be employed to calibrate the rudder 54relative to the rudder controls operated by the aircraft pilot.Calibration establishes the correct relationship by aligning a featureof the rudder (e.g., a centerline) with a feature (e.g., an alignmentindexing plate comprising a plurality of linear measurement markings) onthe rear portion of the fuselage 104. [Similar features (e.g., alignmentindexing plates) may be used to calibrate the elevators 58 a and 58 brelative to the elevator controls operated by the aircraft pilot.] Byrotating the rudder 54 to a target relationship relative to the fuselage104, the location of the rudder feature may be calibrated relative tothe rudder controls. In this manner, the rudder controls may be riggedto accurately reflect the true position of the rudder to improveaircraft performance.

FIG. 17 represents an isometric view of a portion of an empennage havingan alignment indexing plate 112 attached to the top of the rear portionof the fuselage 104 aft of the vertical tail assembly. The vertical tailassembly comprises a vertical stabilizer fairing 126 attached to therear portion of the fuselage 104 by a pair of L-beams 122 and 124 anddisposed directly below the rudder 54 when the latter is in its neutralposition, i.e., a deflection angle of zero degrees. The rudder 54 has alarge bulb seal (not shown in FIG. 14) mounted underneath which rides ontop of the vertical stabilizer fairing 126 for aerodynamic purposes.

The alignment indexing plate 112 is attached at a specified positionusing a pair of indexing plate fasteners 114 and 116. The indexing platefasteners 114 and 116 are considered reference geometry on the aircraftand are precisely located. The alignment indexing plate 112 has aplurality of linear measurement markings 118 thereon which are spacedapart at equal intervals in the manner of a ruler. The alignmentindexing plate 112 is positioned relative to the vertical stabilizerfairing 126 such that a centerline of the rudder 54 will be aligned withan aircraft butt line marking 120 of the plurality of linear measurementmarkings 118 when the rudder 54 is in its neutral position.

One known rudder rigging tool is a heavy block of aluminum (not shown inFIG. 17) that is clamped onto the trailing edge 128 of the rudder 54.The block has a steel pin (not shown) which points to the alignmentindexing plate 112. The rudder 54 can be properly calibrated when thepoint of the steel pin overlies the aircraft butt line marking 120 onthe alignment indexing plate 112. This technique may present a potentialfor observational error beyond the design requirement. In addition, theknown rudder rigging tool must be read at a close distance. Thisrequires a maintenance technician to spend time acquiring and setting upa laptop and webcam system in order to comply with a five-foot hazardousenergy rule with regard to active control surfaces. The rudder riggingtool then remains attached while the rudder is swung in factory testing,presenting a potential risk of detachment.

In accordance with the rudder rigging technique disclosed herein, asensor module 2 (not shown in FIG. 17, but see FIG. 19) may be clampedto the aircraft 100 and utilized to indicate the position of a rudder 54that has an optical target on the trailing edge 128. In accordance withone embodiment depicted in FIG. 13, that optical target may take theform of a reflective tape 142 adhered to an underlying contact tape 144that is approved by the factory for contact with the skin of the rudder54. In this implementation, the sensor module 2 is operated in a floodmode and the microcontroller 20 measures the position of a centerlinelocated between the edges of the optical target in the manner disclosedin U.S. patent application Ser. No. 15/407,076, the disclosure of whichis incorporated by reference herein in its entirety.

FIG. 18 represents a top view of a rudder 54 having a non-neutralposition relative to an alignment indexing plate 112 attached to therear portion of the fuselage 104. Specifically, the dashed line labeledRUDDER CL in FIG. 18 indicates the position of the centerline of therudder 54 relative to the position of the aircraft butt line marking120, which position is represented by the dashed-dotted line labeled BL0.00. This linear position of the rudder centerline in relation to theaircraft butt line is used as an approximation of the angular deflectionof the rudder 54 at small angles close to the neutral position at BL0.00. When the centerline of rudder 54 aligns with the aircraft buttline marking 120 during a rudder rigging operation, the maintenancetechnician on the flight deck can calibrate the rudder controls toindicate that the rudder 54 has a deflection angle of zero degrees.

FIG. 19 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a flood mode)and installed for measuring a position of a rudder 54 relative to thealignment indexing plate 112 shown in FIG. 18. The sensor module 2 isattached to a clamp 4 d that is specially configured for holding thesensor module 2 in a fixed position relative to the rudder 54 of theaircraft 100. In this example, an optical target 146 (of the typedisclosed in U.S. patent application Ser. No. 15/407,076) is attached tothe trailing edge 128 of rudder 54. The optical target 146 includes areflector and a pair of wings made of opaque material disposed onopposite sides of the reflector as described in detail in U.S. patentapplication Ser. No. 15/407,076. The sensor module 2 is used tocalibrate the zero position of the rudder 54 to corresponding positionsof rudder pedals used by the pilot to control the direction (left orright) of yaw about the airplane's vertical axis for minor adjustments.The remote optical control surface indication system does not contactthe moving rudder 54 and is attached securely to the vertical stabilizerfairing 126, indexed to the alignment indexing plate 112 shown in FIG.18.

The clamp 4 d depicted in FIG. 19 includes: a rudder clamp base 148 thatis aligned with alignment indexing plate 112; a pair of rudder clamparms 150 a and 150 b which are clamped to the vertical stabilizerfairing 126 by tightening a pair of thumbscrews 11 having plastic tips;and a rudder clamp block 151 to which the sensor module 2 is latched.The rudder clamp base 148, rudder clamp arms 150 a and 150 b, and rudderclamp block 151 form a rigid support structure designed to hold thesensor module at a specific location (including position andorientation) relative to the vertical stabilizer fairing 126 formeasuring the angular position of the rudder 54. Other arrangements forcalibrating the zero positions of ailerons, flaperons and elevators aredescribed in some detail below.

The clamp 4 d is placed on the rear portion of the fuselage 104 in aposition that overlies and is fixed relative to the aforementionedalignment indexing plate 112. The rudder clamp base 148 comprises a pairof locating mechanisms (not shown in the drawings) which sit on therespective indexing plate fasteners 114 and 116 seen in FIG. 18. In oneimplementation, the locating mechanisms are drill bushings set rigidlyin the rudder clamp base 148 that interface with the heads of theindexing plate fasteners 114 and 116. When the drill bushingsrespectively engage the heads of the indexing plate fasteners 114 and116, the sensor module 2 is thereby located with respect to alignmentindexing plate 112 to a certain degree of precision and repeatability.When the rudder clamp base 148 is properly seated on indexing platefasteners 114 and 116, the maintenance technician knows the preciselocation of the sensor module 2 relative to the aircraft. Morespecifically, the precise location (i.e., position and orientation) ofthe sensor module 2 relative to the axis of rotation of the rudder 54and relative to the centerline of the rudder 54 when it is in itsneutral position (i.e., when the rudder centerline overlaps the baselineBL 0.00 seen in FIG. 18) are known.

FIG. 20 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a laser mode)and installed for measuring a position of an elevator 58 relative to analignment indexing plate 111 attached to the fuselage 104 in accordancewith another embodiment. A sensor module 2 is latched to an elevatorclamp 4 c. The elevator clamp 4 c includes an elevator clamp arm 178that is clamped to a trailing edge of the elevator 58 (using a pair ofthumbscrews 11 a and 11 b) and an elevator clamp block 180 that supportsthe sensor module 2. The sensor module 2 is held in place on theelevator clamp block 180 by a pair of draw latches (only draw latch 160a is visible in FIG. 20). As seen in FIG. 20, the draw latch 160 a ispivotably coupled to an anchor bracket. The other draw latch is alsopivotably coupled to an anchor bracket (not visible in FIG. 20). Theelevator clamp 4 c further includes an indexing pin 165 which is used toplace the elevator clamp 4 c in a specified position relative to theelevator 58. Other indexing pins are not visible in FIG. 20. Theelevator clamp 4 c further includes an indicator flag 176 whichindicates whether the elevator clamp 4 c has been moved subsequent toinstallation on the trailing edge of the elevator 58.

In the rigging scenario depicted in FIG. 20, an optical target 113 isplaced on an alignment indexing plate 111 that is attached to a side ofthe fuselage 104 in proximity to the trailing edge of the elevator 58.The alignment indexing plate 111 indicates the zero position of theelevator 58. The optical target 113 is a lightweight plastic assemblythat has holes to index with the fasteners that attach the alignmentindexing plate 111 to the fuselage 104. The planar upper surface of theoptical target 113 is on a plane flush with the center mark (zeroposition) on the alignment indexing plate 111, and the laser line fromthe sensor module 2 impinges onto that upper surface.

FIG. 21 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a flood mode)and installed for measuring a position of an elevator 58 relative to thealignment indexing plate 111 in accordance with an alternativeimplementation. In this case the LED array inside the sensor module isactivated to flood the alignment indexing plate 111 and adjacent areaswith light and then the object centroid corresponding to the lightabsorbed by the center line of the alignment indexing plate 111 isdetected to determine when the elevator 58 is in its zero position.

It should be noted that in the implementations depicted in FIGS. 20 and21, the sensor module and clamp assembly are affixed to a moving controlsurface, namely, elevator 58 (in other words, the reference surface ismoving and the measurement surface is stationary). In otherimplementations described below, the sensor module and clamp assemblyare affixed to a stationary part of the aircraft (in other words, thereference surface is stationary and the measurement surface is moving).

More specifically, respective clamps are installed on the aircraft formeasuring the zero position of the left and right ailerons 52 a and 52 band the left and right flaperons 56 a and 56 b seen in FIG. 11. Theclamps may be installed onto the aircraft either before or after thesensor modules are attached to the clamps. Clamps are labeled by controlsurface and by letter code, where A=left aileron, B=right aileron,C=left flaperon, and D=right flaperon.

Any sensor module 2 may be attached to any clamp 4 before or after thesensor module 2 is powered on, and the clamps 4 may be attached to theaircraft either before or after the sensor modules 2 are attached to theclamps 4. To attach the sensor module 2, seat the rubber draw latches160 into their respective catches 33 one by one. The two alignmentfeatures will index to two holes in the bottom of the sensor module 2.

To turn a sensor module on, the inspection technician depresses the mainpower button. After the microcontroller has booted for several seconds,the LED and the LCD screen become illuminated. Whenever a sensor isplaced on a clamp, whether powered on before or after attachment, thesensor will automatically begin a countdown and enter into sleep mode bydefault. The sensor will not be ready for measurement until the wakecommand is sent by the DAQ.

FIG. 22 is a diagram representing a three-dimensional view of a remoteoptical control surface indication system configured (in a laser mode)and installed for measuring a position of an aileron 52 relative to afixed trailing edge 53 of a wing 101 b in accordance with yet anotherembodiment. A sensor module 2 is latched to an aileron clamp 4 a, whichis in turn clamped to the trailing edge 53 of wing 101 b by thumbscrews11 (only one thumbscrew is visible in FIG. 22).

FIGS. 23A and 23B are diagrams representing top and bottomthree-dimensional views respectively of an aileron clamp 4 a inaccordance with one proposed implementation. This view shows a left-handaileron clamp, but the right-hand aileron clamp depicted in FIG. 22 issimilar in construction to the left-hand aileron clamp shown in FIGS.23A and 23B. (More specifically, the clamp block is a mirror image, butthe clamp assembly is asymmetrical because the sensor is asymmetricalwith a long end and a short end.) In either case, the aileron clamp 4 ais an assembly that includes an aileron clamp block 152, an inboardaileron clamp arm 154 a and an outboard aileron clamp arm 154 b(hereinafter “aileron clamp arms 154 a and 154 b”). The aileron clamparms 154 a and 154 b are rigidly coupled to the aileron clamp block 152.The aileron clamp arms 154 a and 154 b are made of metal. for example,aluminum. The aileron clamp block 152 is made of polymeric material, forexample, DuPont™ Delrin® acetal resin, which is lightweight and can bemachined to tight tolerances.

Each of the aileron clamp arms 154 a and 154 b has a threaded bore whichthreadably engages the threaded shaft of respective thumbscrews 11 a and11 b. Each of the aileron clamp arms 154 a and 154 b also supportmounting screws with coil springs (not shown in FIGS. 23A and 23B) thathold up a respective polymeric gripping pad 156 (e.g., made ofpolyurethane) and a respective pressure plate 158. When the thumbscrews11 a and 11 b are tightened, the pressure plate 158 presses thepolymeric gripping pad 156 into contact with the bottom surface of thefixed trailing edge of the wing. At the same time, the aileron clampblock 152 (also made of polymeric material) presses against the topsurface of the fixed trailing edge of the wing. Since the clamp surfacesthat contact the trailing edge of the wing are made of polymericmaterial, damage to the wing surface is avoided. In an alternativeimplementation of the inboard clamp arm, the pressure plate 158 andpolymeric gripping pad 156 are omitted in favor of polymeric tipsinstalled to the ends of the thumbscrews 11 a and 11 b.

The aileron clamp 4 a depicted in FIGS. 23A and 23B further includes amounting girder 157 which is fixedly coupled to the aileron clamp block152. A pair of anchor brackets 159 a and 159 b are attached to opposingends of the mounting girder 157. In addition, an RFID puck 155 isattached to the mounting girder 157, occupying a position between theanchor bracket 159 b and the aileron clamp block 152. The RFID puck 155has an RFID tag (not shown in FIGS. 23A and 23B, but see FIG. 5)attached thereto. Typically, the RFID tag is a thin disk that is gluedinto place. For the example depicted in FIGS. 23A and 23B, the RFID tagwould contain information that identifies a left-hand aileron clamp.

A sensor module 2 is anchored to the anchor brackets 159 a and 159 b bymeans of a pair of draw latches 160 a and 160 b. One end of draw latch160 a is pivotably coupled to anchor bracket 159 a; one end of drawlatch 160 b is pivotably coupled to anchor bracket 159 b. The latches160 a and 160 b latch onto the catches 33 a and 33 b (seen in FIG. 8) tosecure the sensor module 2 to the aileron clamp 4 a. The aileron clampblock 152 has sensor alignment geometry 166 a and 166 b affixed theretowhich protrudes from the top surface and engages in correspondingrecesses in the base of the sensor module 2, which engagement ensuresthat the sensor module 2 is correctly located relative to themeasurement surface.

In one implementation, two aileron clamps interface with the fixedtrailing edge of each wing in the area surrounding the fuel jettisonboom. FIG. 24 is a diagram representing a three-dimensional view of anaileron clamp 4 a installed (without a sensor module) on a fixedtrailing edge 23 of a right-hand wing of an aircraft in the areasurrounding a fuel jettison boom 51.

FIG. 25 is a diagram representing a three-dimensional view of a portionof an aileron clamp 4 a in the process of being installed. When thethumbscrew is fully tightened, a portion of the trailing edge 53 of thewing is clamped between the polymeric aileron clamp block 152 and thepolymeric gripping pad 156 to provide a non-marring grip of the paintedsurfaces of the trailing edge 53 of the wing. As seen in FIG. 25, oneend of the draw latch 160 is pivotably coupled to an axle 164 that issupported at opposite ends by a clevis 162. The clevis 162 in turn isattached to an anchor bracket (such as anchor brackets 159 a and 159 bdepicted in FIG. 23A).

In accordance with an additional implementation, sensor modules may beinstalled for use in rigging the left and right flaperons 56 a and 56 bseen in FIG. 11. FIG. 26 is a diagram representing a three-dimensionalview of a remote optical control surface indication system configured(in a laser mode) and installed for measuring a position of a flaperon56 relative to an inboard flap 55. A sensor module 2 is latched to aflaperon clamp 4 b, which is in turn clamped to the outboard edge of theinboard flap 55 by a pair of thumbscrews 11 (only one thumbscrew isshown in FIG. 26). In this implementation, the flaperon clamp 4 bbridges a frangible flap panel 57.

FIGS. 27A and 27B are diagrams representing top and bottomthree-dimensional views respectively of a flaperon clamp 4 b inaccordance with one proposed implementation. This view shows aright-hand flaperon clamp, but the left-hand flaperon clamp is a mirrorimage of the right-hand flaperon clamp shown in FIGS. 27A and 27B. Ineither case, the flaperon clamp 4 b is an assembly that includes aflaperon clamp block 170 and a flaperon clamp arm 168 which is rigidlycoupled to the flaperon clamp block 170. The flaperon clamp arm 168 andflaperon clamp block 170 are made of metal. for example, aluminum. Aflaperon clamp contact pad 172 (visible in FIG. 27B) is attached to theflaperon clamp block 170. The flaperon clamp contact pad 172 is made ofpolymeric material, for example, DuPont™ Delrin® acetal resin.

The flaperon clamp arm 168 has a pair of threaded bores which threadablyengage the threaded shafts of respective thumbscrews 11 a and 11 b. Theflaperon clamp arm 168 also supports mounting screws with coil springs(not shown in FIGS. 27A and 27B) that hold up a respective polymericgripping pad 156 (e.g., made of polyurethane) and a respective pressureplate 158. When the thumbscrews 11 a and 11 b are tightened, thepressure plate 158 presses the polymeric gripping pad 156 into contactwith the bottom surface of the flap 55. At the same time, the flaperonclamp contact pad 172 (also made of polymeric material) presses againstthe top surface of the flap 55. Since the clamp surfaces that contactthe flap 55 are made of polymeric material, damage to the flap surfaceis avoided. The flaperon clamp 4 b depicted in FIGS. 27A and 27B furtherincludes a mounting girder 157 which is fixedly coupled to the flaperonclamp block 170. A pair of anchor brackets 159 a and 159 b are attachedto opposing ends of the mounting girder 157. In addition, an RFID puck155 is attached to the mounting girder 157, occupying a position betweenthe anchor bracket 159 a and the flaperon clamp block 170. The RFID puck155 has an RFID tag (not shown in FIGS. 27A and 27B) attached thereto.For the example depicted in FIGS. 27A and 27B, the RFID tag wouldcontain information that identifies a right-hand flaperon clamp.

A sensor module 2 is anchored to the anchor brackets 159 a and 159 b bymeans of a pair of draw latches 160 a and 160 b as previously described.The latches 160 a and 160 b latch onto the catches 33 a and 33 b (seenin FIG. 8) to secure the sensor module 2 to the flaperon clamp 4 b. Theflaperon clamp block 170 has sensor alignment geometry 166 a and 166 baffixed thereto which protrudes from the top surface and engages incorresponding recesses in the base of the sensor module 2, whichengagement ensures that the sensor module 2 is correctly locatedrelative to the measurement surface.

FIG. 28 is a diagram representing a three-dimensional view of somecomponents of a flaperon clamp 4 b installed on an inboard flap 55. Whenthe thumbscrews 11 a and 11 b are fully tightened, an aft outboardcorner of the inboard flap 55 is clamped between the polymeric flaperonclamp contact pad 172 and the polymeric gripping pad 156 to provide anon-marring grip of the painted surfaces of the inboard flap 55. Theflaperon clamp contact pad 172 is machined down to a specific thicknessafter it is mounted to the flaperon clamp block 170 to maintain thesensor mounting height of ½″ above the measurement surface at theoptimal rigging zero position. The reason the flaperon clamp block 170is made of aluminum in this case is because the flaperon clamp block 170needs to reach over the frangible flap panel 57 where nothing should bemounted, and therefore it needs to be stiff and not sag over its length.

As seen in FIG. 28, one end of the draw latch 160 is pivotably coupledto an axle 164 that is supported at opposite ends by a clevis 162. Theclevis 162 in turn is attached to an anchor bracket (such as anchorbrackets 159 a and 159 b depicted in FIG. 27A). The other end of thedraw latch 160 couples with a catch (not visible in FIG. 28) to hold thesensor module 2 in proper position in relation to the adjacent flaperon56.

The flaperon clamp 4 b is properly placed on the inboard flap 55 withthe aid of three indexing pins 165, only two of which are visible inFIG. 28. FIG. 29 is a diagram representing a bottom view of the indexingof a right-hand flaperon clamp 4 b (with a sensor module 2) clamped tothe outboard corner of an inboard flap 55. As shown in FIG. 29, twoalignment pins 165 a and 165 b must contact the trailing edge of theinboard flap 55, while a third alignment pin 165 c contacts the outboardedge of the frangible flap panel 57. Before tightening the twothumbscrews 11 a and 11 b, the flaperon clamp 4 b is pushed onto theflap assembly until all three of the indexing pins 165 a-165 c aremaking contact with the aircraft skin. Then the thumbscrews 11 a and 11b are hand-tightened, making sure that the indexing pins are stillmaking contact.

During the flaperon rigging procedure, the inboard flap 55 is fullyretracted and rigged (mechanically set) to its precise zero-degreeposition. This is a prerequisite to the rigging of the flaperons, sincethe flaperons are rigged to a certain position in relation to theinboard flap trailing edge. However, the clamp and sensor may beattached to the flap at any time without interfering with the flaprigging process.

In accordance with some implementations, some or all of the clamp armsare equipped with indicator flags to ensure that the clamp has not beenmoved by accident subsequent to installation. FIG. 30 is a diagramrepresenting an end view of an elevator clamp 4 c installed (without asensor module) on a trailing edge of an elevator 58. The elevator clamp4 c features an indicator flag 176 that has a red surface 3 a and agreen surface 3 b. When the elevator clamp 4 c is properly installed onthe trailing edge of the elevator 58, a catch feature 176 a latchesunderneath that trailing edge and the green surface 3 b is visible froma vantage point aft of the trailing edge of the elevator 58. However, ifthe elevator clamp 4 c is moved in a manner that causes the catchfeature 176 a to unlatch from the trailing edge of the elevator 58, aspring 174 applies a torque that causes the indicator flag to rotateclockwise in the view seen in FIG. 30. As a result of this rotation, thegreen surface 3 b is no longer visible from the aforementioned viewpointand instead the red surface 3 a is visible. This provides a visual alertthat the installation of the elevator clamp 4 c should be checked beforestarting the elevator rigging procedure.

One embodiment of a method for optically measuring a position of ameasurement surface relative to a reference position using abattery-powered sensor module includes the following steps. A firstclamp is attached to a first reference surface at a first location,wherein the first clamp has a first structure designed to clamp onto thefirst reference surface at the first location. Before or after the firstclamp is attached, a first sensor module is fixedly coupled to the firstclamp so that a first laser device inside the first sensor module isaimed at a first measurement surface. One of the first measurementsurface and first reference surface is movable relative to the other.Electric power from a first battery incorporated in the first sensormodule is supplied while the first sensor module is in a sleep mode atthe first location. Then a second clamp is attached to a secondreference surface at a second location, wherein the second clamp has asecond structure designed to clamp onto the second reference surface atthe second location. Before or after the second clamp is attached, asecond sensor module is fixedly coupled to the second clamp so that asecond laser device inside the second sensor module is aimed at a secondmeasurement surface. One of the second measurement surface and secondreference surface is movable relative to the other. Electric power froma second battery incorporated in the second sensor module is suppliedwhile the second sensor module is in a sleep mode at the secondlocation.

Following installation of the first and second sensor modules, therespective positions of the first and second measurement surfaces may bemeasured at different times. In accordance with one embodiment of themethod, the mode of the first sensor module is wirelessly changed from asleep mode to an active mode at a first time. The second sensor moduleis in the sleep mode at the first time. Then the first sensor module inthe active mode is wirelessly activated to project a curtain of lightonto the first measurement surface along a first impingement line usingthe first laser device and detect a first object centroid where lightscattered from the first impingement line impinges on a first row ofphotodetectors of the first sensor module. The first object centroiddata signals are wirelessly transmitted from the first sensor module toa data acquisition module (e.g., data acquisition computer 62). Thefirst object centroid data signals represent a measured position of thefirst measurement surface at the first time.

Thereafter the mode of the second sensor module is wirelessly changedfrom a sleep mode to an active mode at a second time. In the interimbetween the first and second times, the first sensor module iswirelessly changed from the active mode to the sleep mode. Thus thefirst sensor module is in the sleep mode at the second time. Then thesecond sensor module in the active mode is wirelessly activated toproject a curtain of light onto the second measurement surface along asecond impingement line using the second laser device and detect asecond object centroid where light scattered from the second impingementline impinges on a second row of photodetectors of the second sensormodule. The second object centroid data signals are wirelesslytransmitted from the second sensor module to the data acquisitionmodule. The second object centroid data signals represent a measuredposition of the second measurement surface at the second time.

The data acquisition module converts the first object centroid datasignals to a first distance measurement using first stored datarepresenting a table or an equation that correlates pixel values withmeasured distances in a manner that is characteristic of movement of thefirst measurement surface. Likewise data acquisition module converts thesecond object centroid data signals to a second distance measurementusing second stored data representing a table or an equation thatcorrelates pixel values with measured distances in a manner that ischaracteristic of movement of the second measurement surface.

The procedure described in the immediately preceding four paragraphs maybe extrapolated to include the installation of more than two sensormodules on a structure. For example, a multiplicity of sensor modules 2may be installed on an aircraft at the locations indicated in FIG. 12and employed in the rigging of the ailerons, flaperons, elevators,rudder and other control surfaces of the aircraft.

While systems and methods for optically measuring a position of ameasurement surface relative to a reference position have been describedwith reference to various embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the teachingsherein. In addition, many modifications may be made to adapt theconcepts and reductions to practice disclosed herein to a particularsituation. Accordingly, it is intended that the subject matter coveredby the claims not be limited to the disclosed embodiments.

The embodiments disclosed above use one or more computing systems. Asused herein, the term “computing system” comprises one or more of thefollowing: a computer, a processor, a controller, a central processingunit, a microcontroller, a reduced instruction set computer processor,an ASIC, a programmable logic circuit, an FPGA, a digital signalprocessor, and/or any other circuit or processing device capable ofexecuting the functions described herein. For example, a computingsystem may comprise multiple microcontrollers or multiple processorswhich communicate via interfaces.

The methods described herein may be encoded as executable instructionsembodied in a non-transitory tangible computer-readable storage medium,including, without limitation, a storage device and/or a memory device.Such instructions, when executed by a processing or computing system,cause the system device to perform at least a portion of the methodsdescribed herein.

As used herein, the term “location” comprises position in a fixedthree-dimensional coordinate system and orientation relative to thatcoordinate system. As used in the claims, the term “support member”should be construed broadly to encompass a plunger boss and structuralequivalents thereof.

The structure corresponding to the “means for identifying the clamp”recited in the claims includes an RFID tag, physical featuresrecognizable by a microswitch array, and structural equivalents thereof.

The invention claimed is:
 1. A method for optically measuring a positionof a measurement surface relative to a reference position, the methodcomprising: (a) clamping a laser device to a reference surface so thatthe laser device is aimed at a measurement surface which is movablerelative to the reference surface; (b) projecting a curtain of light ina first plane from the laser device that impinges upon the measurementsurface to form a laser line that includes a slice, wherein a portion ofthe impinging light that forms the slice of the laser line is scatteredby the measurement surface toward and then impinges upon photodetectorsof a row of photodetectors with an intensity that rises and falls andpeaks at a center of the light from the slice of the laser line whichimpinges upon the photodetectors; (c) locating an object centroid inunits of pixels based on pixel data acquired by the row ofphotodetectors during impingement of the light from the slice of thelaser line which impinges upon the photodetectors, wherein the objectcentroid represents a location on the row of photodetectors of peakintensity of the light from the slice of the laser line; and (d)transmitting object centroid data signals that represent a measuredposition of the measurement surface relative to the reference surface.2. The method as recited in claim 1, wherein step (a) comprisesorienting the row of photodetectors so that the row of photodetectorsare aligned in a second plane that is generally perpendicular to thefirst plane and intersects the curtain of light.
 3. The method asrecited in claim 1, wherein step (c) comprises: finding an intensitybaseline and peak; correcting light intensity for lens vignetteartifact; interpolating pixel data for pseudo-sub-pixel resolution;object detection thresholding; and calculating the object centroid. 4.The method as recited in claim 1, further comprising converting theobject centroid data signals to a distance measurement using stored datarepresenting a table or an equation that correlates pixel values withmeasured distances in a manner that is characteristic of relativemovement of the measurement surface and reference surface.
 5. The methodas recited in claim 1, wherein the reference surface is a controlsurface of an aircraft.
 6. The method as recited in claim 5, furthercomprising attaching an optical target comprising the measurementsurface to a fuselage of the aircraft.
 7. The method as recited in claim1, wherein the measurement surface is a first control surface of anaircraft.
 8. The method as recited in claim 7, wherein the referencesurface is a second control surface of the aircraft.
 9. The method asrecited in claim 7, wherein the reference surface is a surface of afuselage of the aircraft.
 10. The method as recited in claim 7, whereinthe reference surface is a surface of a wing of the aircraft.
 11. Themethod as recited in claim 1, wherein the measurement surface is acontrol surface of an aircraft, the method further comprising: rotatingthe control surface by discrete degrees of actuation; repeating steps(b) and (c) at each discrete degree of actuation until the measuredposition of the control surface relative to the reference surface is aneutral position; and rigging operator controls to accurately reflectthe neutral position of the control surface.
 12. The method as recitedin claim 1, wherein the reference surface is a control surface of anaircraft, the method further comprising: rotating the control surface bydiscrete degrees of actuation; repeating steps (c) and (d) at eachdiscrete degree of actuation until the measured position of the controlsurface relative to the measurement surface is a neutral position; andrigging operator controls to accurately reflect the neutral position ofthe control surface.
 13. A wireless network used to practice the methodas recited in claim 1, the wireless network comprising: a computersystem that hosts data acquisition software configured to convert objectcentroid data into distance measurement data; a central transceiveroperatively coupled to the computer system for receiving aradio-frequency signal carrying the object centroid data andtransmitting the object centroid data to the computer system; and asensor module located within communication range of the centraltransceiver, wherein the sensor module comprises: a housing; a battery;a laser device mounted inside the housing and configured to project acurtain of light in a first plane; a row of photodetectors arranged insequence along a straight line inside the housing and configured tooutput respective analog photodetector output signals in response toimpingement of light; a lens mounted inside the housing in front of therow of photodetectors and having a focal axis, wherein a field of viewof the lens intersects the curtain of light; and wherein the focal axisof the lens and the straight line of the row of photodetectors lie in asecond plane that is perpendicular to the first plane; a microcontrollerthat is configured to control operation of the laser device and computea location of an object centroid relative to the row of photodetectorsbased on the analog photodetector output signals output by the row ofphotodetectors; and a transceiver configured to transmit aradio-frequency signal carrying object centroid data representing thelocation of the object centroid computed by the microcontroller, whereinthe laser device, the microcontroller and the transceiver receiveelectric power from the battery.
 14. The wireless network as recited inclaim 13, wherein the sensor module is clamped to a surface of anaircraft.
 15. The wireless network as recited in claim 13, wherein themicrocontroller is configured to control operation of the laser deviceto project a curtain of light in the first plane from the laser deviceonto a measurement surface to form an impingement line.
 16. The wirelessnetwork as recited in claim 15, wherein the microcontroller is furtherconfigured to detect an object centroid where light scattered from theimpingement line impinges on the row of photodetectors.
 17. The wirelessnetwork as recited in claim 16, wherein detecting an object centroidcomprises: finding an intensity baseline and peak; correcting lightintensity for lens vignette artifact; interpolating pixel data forpseudo-sub-pixel resolution; object detection thresholding; andcalculating the object centroid.
 18. The wireless network as recited inclaim 16, wherein the microcontroller is further configured to sendobject centroid data that represent a measured position of themeasurement surface relative to a reference surface to the transceiver.19. The wireless network as recited in claim 18, wherein the computersystem is configured to convert the object centroid data signalsreceived from the transceiver to a distance measurement using storeddata representing a table or an equation that correlates pixel valueswith measured distances in a manner that is characteristic of relativemovement of the measurement surface and reference surface.
 20. Thewireless network as recited in claim 13, wherein the sensor module isoriented so that the row of photodetectors are aligned in a second planethat is generally perpendicular to the first plane and intersects thecurtain of light.